Why fliers really do need to turn off electronic devices
— -- "What part of 'please turn your cellphone off' do you feel does not apply to you?" Peter Juhren asked a fellow passenger as their New York-bound Delta Air Lines flight taxied for takeoff Dec. 7 at Tampa's airport.
Juhren, a frequent business traveler from Salem, Ore., says the woman on the phone gave "a disgruntled look" but stopped talking and turned it off — after three times ignoring a flight attendant's request to do so.
Passengers have blamed airlines and the government for safety problems for decades, but now they might have to share some blame.
A USA TODAY investigation shows that passengers are frequently disregarding flight attendants' instructions to turn off portable electronic devices during takeoff and landing — two critical flight phases when a mistake by a pilot could lead to an accident.
Many passengers question the rationale behind shutting off electronic devices in-flight, but the investigation's review of thousands of pages of technical documents shows the gadgets emit radio signals that can interfere with cockpit instruments and electronic equipment and systems on an aircraft.
"Any device with a battery — including cellphones, e-readers, laptops, PDAs (personal digital assistants) and Game Boys — has some level of emission that has the potential to interfere with cockpit instruments or navigational equipment," says Boeing engineer Dave Carson.
Technical committees have evaluated many portable electronic devices and found the margin of safety is not sufficient to allow passengers to use them during takeoff and landing, says Carson, co-chairman of an RTCA committee that studied portable electronic devices on aircraft.
RTCA is a non-profit corporation that develops communications and navigation recommendations for the Federal Aviation Administration.
Carson says most devices used "in aggregate or independently" by passengers would not meet the RTCA's DO-160 standard, which sets emission standards for airborne equipment.
Electronics experts say they do not have such electromagnetic interference (EMI) concerns about an increasing number of Wi-Fi and entertainment systems installed by aircraft manufacturers and airlines, because those systems are thoroughly tested to meet standards.
EMI-related documents reviewed by USA TODAY include more than 25 papers by electronics experts; presentations, papers and advisories by government aviation officials in the USA, Canada, the United Kingdom and Europe; congressional testimony; and Boeing research and information for airlines.
Some findings:
•A 2008 RTCA study, considered the most recent definitive one on the subject, confirmed that spurious emissions from transmitting portable electronic devices onboard aircraft "could exceed interference thresholds for critical aircraft systems."
RTCA, which gave USA TODAY permission to access the study, says an aircraft's localizer and glide-slope systems — two systems used for landing — "show potential susceptibility to continuous wave interference," supporting the "prohibition on the use of portable electronic devices below 10,000 feet."
The operation of portable electronic devices "changes the electromagnetic environment" of aircraft radio receivers and "may introduce additional interference effects."
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